How should we go about buying a house?

Alright, I am needing some advice on our situation from those who have been through something similar or have helped people with it.

My fiancé and I want to buy a house but his credit is. Not so good. We are disputing stuff his old mortgage company put on his credit after he sold his house but it is taking forever. Its been since October 2015 since he filed disputes and reported them to the FDIC.
His credit now I believe is in the low 600s and he has no debt. Mine is about 685. My credit is still fairly new but the history is great. No bad marks, No late payments, almost no balances, Etc. I have a lot of credit available to me as well because of my great history. Our monthly income is about 6,000 a month and we would have no problem paying for a mortgage. We also have great rental history from a private renter.

The house we are looking to build is about 316,000 but we have no idea what to do about our situation. What do we do? We hate having to rent and worry about where we are going next. Especially when we have a 2 year old. We want to be able to have our own home and not have to move around all the time.

Sorry if this seems all over the place, I'm just worried about what to do. If anyone has any input or something that will help us It would be greatly appreciated.

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